1. Field
The present invention relates to a reagent composition for a biosensor having high sensitivity, which is capable of improving analysis linearity of an analyte such as glucose, detecting a concentration of a small amount of analyte, and minimizing blood necessary for measuring blood glucose, and a biosensor having the same.
2. Discussion of Related Art
The present invention relates to a reagent composition for a biosensor and a biosensor having the same, and particularly, to a reagent composition for quantifying a specific ingredient of a biological sample and a biosensor having the same.
Recently, as the number of diabetic patients increases, necessity of periodically measuring an amount of blood glucose has been increased in order to diagnose and prevent diabetes. Such diabetes is known as a major health risk factor. In general, American Diabetes Association (ADA) recommends that most insulin-dependent diabetic patients check the blood glucose three or more times per day. Insulin controls use of blood sugar and prevents hyperglycemia that may cause ketosis when diabetes is not treated. However, inappropriate management of an insulin therapy may cause hypoglycemia. Since hypoglycemia may cause a coma, it may be fatal for patients.
In addition, when patients suffer from diabetes for a long time, complications such as heart disease, atherosclerosis, blindness, a stroke, hypertension, and renal failures may be caused. Since an amount of insulin injection is associated with an amount of the blood glucose, accurate detection of the blood glucose is essential to appropriately treat diabetes.
Accordingly, various blood glucose meters are produced such that the blood glucose may be easily measured using portable instruments. In general, in the blood glucose meters, each user uses a strip-type biosensor. An operating principle of such a biosensor is based on an optical method or an electrochemical method.
The biggest feature of the electrochemical method among these methods is using an electron transfer mediator. As the electron transfer mediator, ferrocene, derivatives of ferrocene; quinone, derivatives of quinone; transition metal-containing organic and inorganic materials (such as hexaammineruthenium, an osmium-containing polymer, and potassium ferricyanide); and electron transfer organic materials such as an organic conducting salt and viologen may be used.
A measurement principle of blood glucose using the electrochemical method is as follows. First, the blood glucose is oxidized to gluconate due to a catalytic action of a glucose oxidase. At this time, FAD, which is an active site of the glucose oxidase, is reduced and became FADH2. Then, the reduced FADH2 is oxidized to FAD through an oxidation-reduction reaction with the electron transfer mediator, and the electron transfer mediator is reduced. Electrons generated from the electron transfer mediator in a reduction state formed in this manner disperse to an electrode surface. At this time, a concentration of the blood glucose is measured by measuring a current generated by applying an oxidation potential of the electron transfer mediator in a reduction state in a working electrode surface.
Unlike a biosensor using a conventional optical method, an electrochemical biosensor using the above measurement principle may reduce an influence of oxygen, and even when sample is turbid, it is possible to use the sample without separate pretreatment.
In addition, a general electrochemical biosensor is made such that an electrode system including a plurality of electrodes is formed on an electrically insulating substrate using a method such as screen printing, and an enzyme reaction layer made of a hydrophilic polymer, an oxidoreductase, and an electron accepter is formed on the formed electrode system. When a sample solution including a substrate is dropped onto the enzyme reaction layer of the electrochemical biosensor, the enzyme reaction layer is dissolved, the substrate reacts with the enzyme, the substrate is oxidized, and therefore the electron accepter is reduced. After the enzyme reaction is completed, a concentration of the substrate in the sample solution may be obtained from an oxidation current that is obtained by electrochemically oxidizing the reduced electron accepter.
When such a biosensor is used, accurately and rapidly obtaining a measurement value using a small amount of a sample is a very important issue in terms of maximizing a user's convenience. Most products for measuring the blood glucose use a method of sampling blood and then quantifying the blood glucose in blood using a biosensor. However, since blood sampling is a considerably painful operation for the patient, it is necessary to minimize an amount of blood necessary for measurement in order to reduce the patient's pain. In particular, when 1 μl or less of a small amount of a sample is used, preferably 0.5 μl or less of a sample, and more preferably, 0.3 μl or less of a sample is used, since it is possible to sample and measure blood from an alternative site such as a forearm, it is possible to minimize resulting pain when the patient measures the blood glucose. Therefore, the biosensor needs to minimize an amount of blood necessary for measuring the blood glucose.
In addition, another issue of the biosensor is reduced measurement sensitivity according to miniaturization. An amount of a reaction-related material fixed to the electrode surface is one of major factors influencing sensitivity of the biosensor. However, recently, as the biosensors are gradually miniaturized, an area to which materials to react with a specific material may be fixed also decreases. Accordingly, there is a serious limitation of the development of a compact sensor having high sensitivity.